1. Field of the Invention
The present invention relates to a method of identifying a direction of stacking in a stacked ceramic capacitor, an apparatus for identifying a direction of stacking in a stacked ceramic capacitor, and a method of manufacturing a stacked ceramic capacitor.
2. Description of the Related Art
A stacked ceramic capacitor has a plurality of internal electrodes stacked in one direction. Therefore, in connection with the stacked ceramic capacitor, there is a demand for identifying a direction in which the internal electrodes are stacked. For example, however, when a stacked ceramic capacitor has a square prism shape, it is difficult to identify based on appearance a direction in which internal electrodes are stacked in the stacked ceramic capacitor.
For example, Japanese Patent Laying-Open No. 7-115033 describes a method allowing identification of a direction in which internal electrodes are stacked in a stacked ceramic capacitor, regardless of appearance. Specifically, Japanese Patent Laying-Open No. 7-115033 discloses a method of measuring magnetic flux density in a stacked ceramic capacitor by applying a certain magnetic field to one surface to which an internal electrode layer is not extracted and identifying a direction in which internal electrode layers are stacked based on intensity of magnetization. This method makes use of a difference in measured magnetic flux density between a state in which a capacitor is arranged in an orientation in which internal electrodes are substantially in parallel to a magnetic flux (as a capacitor, internal electrodes extend in a direction perpendicular to a bottom surface) and a state in which a capacitor is arranged in an orientation in which the internal electrodes are substantially perpendicular to the magnetic flux (as a capacitor, internal electrodes are in a direction parallel to a bottom surface).
A difference in measured magnetic flux density, however, is very small, between a case in which a direction of stacking of internal electrodes is parallel to a direction of magnetic flux and a case in which a direction of stacking of internal electrodes is perpendicular to a direction of magnetic flux. In addition, measured magnetic flux density is greatly dependent on a positional relationship between a magnet, and a sensor probe and a capacitor. In particular, in a small stacked ceramic capacitor, an influence caused by a positional relationship between a magnet, and a sensor probe and a capacitor on measured magnetic flux density is significant.
Thus, since a difference in magnetic flux density measured at the time when a direction is different is small and the measured magnetic flux density is significantly different depending on a position of a capacitor at the time of measurement, it is difficult to accurately identify a direction in a stacked ceramic capacitor with the method described in Japanese Patent Laying-Open No. 7-115033.
This issue will more specifically be described. For example, a case in which a magnetic flux density for a stacked ceramic capacitor having a length dimension of 1 mm, a width dimension of 0.5 mm, and a height dimension of 0.5 mm and having a capacitance of 4.7 μF is measured under certain measurement conditions is assumed. Maximum magnetic flux density of this stacked ceramic capacitor in a case in which a direction of stacking of internal electrodes is parallel to a direction of magnetic flux is approximately 53.6 mT. On the other hand, the maximum magnetic flux density of this stacked ceramic capacitor in a case in which a direction of stacking of internal electrodes is perpendicular to a direction of magnetic flux is approximately 52.3 mT. Therefore, in this stacked ceramic capacitor, a maximum value of magnetic flux density is different only by 1.3 mT between a case in which the direction of stacking of the internal electrodes is parallel to the direction of magnetic flux and the case in which the direction of stacking of the internal electrodes is perpendicular to the direction of magnetic flux. Thus, a difference in maximum value of magnetic flux density between the case in which the direction of stacking of the internal electrodes is parallel to the direction of magnetic flux and the case in which the direction of stacking of the internal electrodes is perpendicular to the direction of magnetic flux is only 2.4% with respect to the maximum value of magnetic flux density in the case in which the direction of stacking of the internal electrodes is parallel to the direction of magnetic flux.
In addition, a magnetic flux density of a stacked ceramic capacitor in which a direction of stacking of internal electrodes is parallel to a direction of magnetic flux at the time when a measurement position for the stacked ceramic capacitor is displaced by 0.3 mm from a central position of the stacked ceramic capacitor is approximately 52.3 mT, and it is substantially equal to the maximum value of magnetic flux density of the stacked ceramic capacitor (when a measurement position is at a central position of the stacked ceramic capacitor) when the direction of stacking of the internal electrodes is perpendicular to the direction of magnetic flux. Thus, when a measurement position for a stacked ceramic capacitor may change by 0.3 mm or more, it is difficult to identify a direction in a stacked ceramic capacitor. This issue is more noticeable because it becomes difficult to set a measurement position to a central position as a stacked ceramic capacitor is reduced in size, for example, when the stacked ceramic capacitor has a 1005 size or smaller having a length dimension of 1 mm, a width dimension of 0.5 mm, and a height dimension of 0.5 mm.